The purpose of this four-year study is to learn more about the use of club drugs, specifically ecstasy, among young adult users in the United States. To gain a better understanding of the careers of ecstasy users, we propose to conduct a study among 300 users. The stages typically involved in drug careers are initiation, including initial avoidance, continuation, escalation/abuse, and maintenance or dependence. Little is known about factors that might motivate or hinder users in moving from one stage to another. Ecstasy is an arousal drug that yields different unsafe sex than the HIV sex risks common with barter drugs such as crack cocaine. Little is known about the HIV risk and protective behaviors among the users of club drugs. The specific aims of the proposed study are: (1) to examine if the career perspective of drug use applies to ecstasy use among young adults, who are active users and who are not in drug treatment. This includes an emphasis on first time use, continued use, changes in use patterns, as well as belief, motivations and perceived advantages and disadvantages of use; (2) to explore factors that hinder or encourage the transition from one stage of use to another. By taking an ecological approach, we acknowledge the impact of individual characteristics as well as contextual circumstances; and (3) to investigate the nature of HIV risk-taking among young adult ecstasy users. The data collection will be primarily qualitative, with some quantitative data collection on demographics and risk behaviors such as drug use, sexual activity, and HIV. Qualitative data analysis involved grounded theory and the quantitative data analysis will be limited to descriptive statistics. The study will be among the first to document in detail the meaning of ecstasy use, the developmental progression of ecstasy use, and motivators and barriers to becoming more frequent users. The existing, although limited literature, on ecstasy suggests users to be at risk for HIV/AIDS. The study findings have the potential to produce information that is useful for social and health service providers, law enforcement officials, policy makers, and others. The study will also provide baseline data for future large-scale studies as well as interventions. We also expect to be able to collect information that can be used for technology transfer.